We all know that when it comes to household electrical lighting, LED lights consume the least amount of energy for a given amount of light, followed by fluorescent tubes, halogens, and Edison-age tungsten-filament light bulbs.
We also know that roughly the same ordering applies when looking at endurance; LED's will last until the end of the universe, flurescent tubes will last thousands of hours, etc.
We've also all seen the graphs that show how much money you'll save for all of these types of electrical lighting. Looking at initial investment (purchase) and energy consumption over a year, the break-even point when compared to tungsten-filament bulbs lies for LED lights somewhere in the order of ~10-15 months, fluorescent tubes ~6 months and halogens ~4 months.
This is all very nice, but this all has a nasty sales-pitch/green-washed marketing aftertaste in all of this; way too much focus is on cost for the consumer, and very little is being said on actual overall energy expenditure.
I want to prove to myself and everyone else that LED's are really the way to go.
What I mean is the following. I would like to create a graph, plotting total energy consumption versus time (so money is not considered), with four lines in them (one for each of the aforementioned types), that takes into account:
The energy it takes to create a single bulb. See this related question. For example, to create a tungsten-filament light bulb, you need tungsten, glass, some metals, some plastics, a mixture of specific gases, cardboard and plastics for the packaging, ... Extraction/production/transportation of these materials takes an amount of energy per kg. Shaping it into a filament/glass housing/metal fitting/etc. takes an amount of energy, etc. In other words, from the "stuff that's in the ground" to "finished product in the store".
Replacement time (this is why LED's will probably have a smooth line, and tungsten-filament bulbs-line will probably show frequent upward jumps due to replacement). The nominal amount of burn hours stated on the packages (mean time before failure, MTBF) is not really sufficient here; these are averages somehow, and frequently come from calculations or laboratory setups rather than actual real-life usage (how else can they claim that LED's can be lit for 10 years continuously?). Also, there is a finite chance that the average user will accidentally drop the bulb, crash into it with a ladder, etc, which is far worse for tungsten-filament bulbs and luminescent tubes than for LED's in protective casings. So, a far more realistic statistical model should be assumed here, which I can't find any reliable, authorative sources for...
Energy expenditure due to disposal and/or recycling
Transportation. This is a broad topic and strongly depends on geographical location, but let's assume some worst-case scenario (where tungsten-filament bulbs have the advantage)
anything else I've forgotten :)
Of course, such detailed calculations can only be done when making some assumptions. Let's assume:
- the most energy-efficient, state-of-the-art models for each kind
- specific models with an equal or at least comparable amount of lumens produced (say, equivalent to a 40W tungsten bulb)
- Daily average use of 5 hours in Winter, 2 hours in summer, sinusoidal in between (or some better, comparable model)
I find it very hard to find sufficient details on this subject to be able to do this comparison. I find it hard to believe that I'm the only one thinking this, but I'm just not finding them.
Does anyone know some sites or papers I should look into?